1. Field of the Invention
The present invention is related to a method and an apparatus for incinerating waste gas generated in a chemical or refinery plant. More specifically the present invention is directed to a method and an apparatus for increasing the incineration capacity of the ground flares by using the principle of tornado, while maintaining the ground flare""s main advantage, that is the ability to insulate the flaring smoke and noise from being observed and heard in the neighborhood of the ground flares.
Generally, a large amount of waste gas is produced when a process in chemical or refinery plant stops or re-starts. A flare system is an essential utility for most chemical plant, which is a device to convert the waste gas into a less harmful form before discharging the waste gas into the ambient air.
2. Description of the Prior Art
The ground flare illustrated in FIGS. 3a and 3b is a flare system adapted for a chemical plant. The basic construction of the ground flare consists of two circular tubes, i.e., a taller inner tube 10 and a shorter outer tube 12, which encloses the bottom portion of the inner tube 10.
The inner tube 10 serves as the wall of the combustion chamber for the waste gas incineration. An air passage is formed along the peripheral space between the inner tube and outer tube. The air, which first passed over the top of the shorter outer tube, enters the annular space between the inner and outer tubes, and then enters the combustion region inside the inner tube through the vertical air inlet placed along the periphery of the bottom of the inner tube. A combustor stack 14 is placed just inside of each vertical air inlet of the inner tube.
In each combustor stack 14, a plurality of combustion nozzles are placed facing the center of the combustion chamber in the vertical direction. The waste gas is injected through each combustion nozzle toward the center of the combustion chamber and is incinerated by the flames attached to the nozzles. The main function of the tube 10 is to form a space for the combustion chamber. At the same time, the inner tube 10 is adapted for preventing the smoke and noise, generated during the flaring operation, from being transmitted to the exterior of the combustion chamber. The outer tube 12, which encloses the lower end of the inner tube, shields the people working in the vicinity of the ground flare from the flare radiation. In addition, the outer tube also protects the flames from being blown away by the wind.
In comparison with the other types of flare systems, the ground flare provides the advantage of preventing the flaring smoke and noise from being transmitted to the exterior of the combustion chamber. The ground flare accomplishes this by using the inner tube as a constitutional element of the flare apparatus. Thus, it is possible to, in effect, mitigate the audiovisual environmental problems occurring during the flaring operation.
However, as seen from FIGS. 3a and 3b, the combustion chamber, in which the waste gas is incinerated, is shielded by the inner tube 10 and outer tube 12. Furthermore, the air required for incineration is introduced through the narrow space between the inner tube 10 and the outer tube 12. Therefore, the air supply in the ground flare system is less efficient than the air supply in the other types of flares that carry out incineration in an open space.
Because of the relatively poor air supply to the combustion region, the ground flare has a lower incineration capacity per the amount of investment and per the installation area than the other types of open space flares have. Thus, in order to obtain a similar incineration capacity to that of open space flare systems, a higher facility cost is required, which is a drawback of the ground flare. Also, a relatively large amount of flaring smoke can be generated due to the deficiency of the air introduced into the combustion chamber.
The present invention was devised in consideration of the problems stated above. It is an object of the present invention to provide a method and an apparatus for increasing the incineration capacity of the ground flare, while preventing the flaring smoke and noise from escaping the combustion chamber, by employing the principle of tornado.
To this end, the method for incinerating the waste gas according to the present invention comprises the steps of:
(a) discharging the waste gas into the combustion chamber and incinerating said waste gas, and
(b) introducing the swirl into the air supply for applying a swirl force to the combustion gas that is elevated by buoyancy.
The apparatus for incinerating waste gas according to the present invention comprises:
a plurality of combustion nozzles 20 stacked vertically just inside of the vertical opening of an inner tube for discharging the waste gas into the combustion chamber,
an incineration inner tube 30 for containing the flare light, flare smoke and flare noise, generated during incineration of the waste gas discharged from the combustion nozzle 20, in the combustion chamber
a plurality of air inlets 32 at the lower periphery of the inner tube 30, and
an outer tube 40 for introducing the swirling air into the combustion chamber to apply a swirl force to the combusted gas that is elevated by buoyancy, said outer tube 40 is provided with several air inlets 42 formed in connection with the incineration inner tube 30 in the tangential direction.